Myofascial pain is associated with the formation of pain "trigger" points or defined areas within a muscle block that exhibit tenderness and abnormal tightness. Acupuncture is an alternative approach to releasing trigger points, thus relieving pain and the associated muscle tension in many cases. Although this therapeutic approach is efficacious there is little scientific evidence to support the clinical relief shown following treatment. DBEPS designed and developed an acupuncture needle with a hollow stem through which a twin tube microdialyzer could be inserted. The exterior bore of the needle was 28 - 30 gauge stainless surgical steel, with one end beveled into a blunt, non-cutting tip by micro-polishing. A 100,000 m.w. cutoff dialyzer membrane was attached to a 30-gauge poly-ether-ether-ketone (PEEK) biocompatible tubing and a 33-gauge PEEK tubing inserted into the first tube, thus forming a inlet and return flow-path terminating in the dialyzer membrane. This apparatus was fixed inside the stainless steel tubing so that the dialyzer surface was flush with the hole in the needle tip. A handle was fixed to the other end of the needle allowing the operator to manipulate the needle in a similar manner to a solid acupuncture needle. Three groups of patients, two with various degree of muscle pain and tension plus controls were recruited to the study. The acupuncture needle was inserted in the shoulder muscle by a skilled acupuncture specialist and samples taken, via microdialysis, from the needle tip. The samples were collected and analyzed for a variety of analytes such as blood gases, cytokines, hormones, neuropeptides, and electrolytes by the DBEPS Ultramicro Analytical Immunochemistry Resource, using established techniques (capillary electrophoresis, capillary electrochromatography, micro-ion selective electrochemistry and micro gas sensors). This project is recruiting subjects under an IRB-approved protocol and analyses are ongoing. The outcome from this project will provide new scientific data on the biochemical and cellular events taking place during acupuncture and during the firing of muscle "trigger" points during the alleviation of pain.